The invention relates to a unit in accordance with the species of claim 1 for conveying fuel from a tank to the internal combustion engine of a motor vehicle.
Such a unit is known from DE 40 20 521 A1. This unit has a conveying pump designed in the form of a flow pump, whose impeller wheel, which is rotatingly driven by a drive element, turns in a pump chamber. The pump chamber is delimited in the direction of the axis of rotation of the impeller wheel by two oppositely located front walls, and in the radial direction in relation to the axis of rotation by an annular wall. On both its front faces, the impeller wheel respectively has a crown of vanes. At the two front walls, grooves are arranged around the axis of rotation of the impeller wheel at the height of the vanes respectively extending over a portion of the circumference which, together with the vanes of the impeller wheel, respectively constitute a conveying channel. The conveying channels lead from an inlet opening on their one end to an outlet opening at their other end. The impeller wheel has an outer ring connecting its vanes at their outward extending ends. With this embodiment of the unit it has been shown that, because of convection, the entry of dirt particles into the space between the outer ring of the impeller wheel and the annular walls through axial gaps existing between the front ends of the impeller wheel and the front ends cannot be ruled out. This is caused by a build-up of pressure occurring in the conveying circuits in the direction of rotation of the impeller wheel, so that therefore a higher pressure exists there than in the space between the outer ring of the impeller wheel and the annular wall, becauseof which an amount of leakage flows from the conveying channels into the annular space. Entry of dirt particles into this chamber can lead to increased wear of the unit and should therefore be avoided.